1. Field of the Invention
The present invention relates to an assembly formed by an adapter for a contact smart card and by the corresponding smart card, the adapter being intended to convert a first smart card format into a second smart card format.
2. Description of the Related Art
In particular, two standardized smart card formats exist for SIM (Subscriber Identity Module) cards, referenced in the ETSI 102 221 v.8.2.0 and ISO7816 standards:                The 2FF format, also called ID-000, wherein the card body is delimited by a rectangular shape of 15 mm×25 mm×0.76 mm, with a shape key of 3×3 mm in one corner of the card body, and        The 3FF format, also called Mini UICC, wherein the card body is delimited by a rectangular shape of 15 mm×12 mm×0.76 mm, with a shape key of 2.5×2.5 mm in one corner of the card body.        
A larger card also exists, with the 1FF format also called ID-1, wherein the card body is delimited by a rectangular shape of 85.6 mm×54 mm×0.76 mm.
1FF, 2FF and 3FF cards comprise a plate, called a contact plate. This contact plate is generally equipped with eight contact surfaces commonly designated by the names C1 to C8. These contact surfaces can be distributed over two substantially parallel columns. A first column can comprise contacts C1 to C4 and a second column can comprise contacts C5 to C8. The ISO7816 standard specifically defines the dimensions of minimum contact areas that these contact surfaces must have, namely 2 millimeters long and 1.7 millimeters wide (by convention, the length is measured parallel to the largest dimension of the card and the width perpendicularly to this dimension). This standard also defines the positions relative to these contact areas as well as their dimensionings and positionings with respect to the card body. The contact surfaces, commonly called ISO contacts when they comply with the aforementioned ISO standard, have the aim of providing the electrical connection between an electronic chip, integral with the card, and a reading/writing device.
In practice the contact surfaces extend on each side beyond the contact areas defined by the standards, for example over distances substantially equal along the length, or along the width; it is then said that the contact areas are substantially centered on the contact surfaces (which equates to saying that the middles, of the width or of the length, are superimposed).
Thus, the contact surfaces correspond to effective surfaces whereas the contact areas correspond to the minimum theoretical sites described by the ISO7816 standard.
By way of information, the contact surfaces C1 and C5 are used for the power supply, where C1 corresponds to Vcc, also called “positive power supply” and C5 corresponds to GND, also called “ground”.
The contact surface C2, also called RST, is used to reset the chip to zero.
The contact surface C3, also called CLK, acts as the clock of the chip.
The contact surface C7, also called I/O, is used for the inputs and outputs of the chip information.
The contact surfaces C4, C6 and C8 are intended for so-called “reserved” contacts, which have no particular functions. Today, these contacts C4 and C8 can be used for USB ports and the contact C6 for the SWP (Single Wire Protocol) communication protocol.
In the remainder of the description, it may be considered that contacts having an index have the same functions as those described above.
In the remainder of the description it will be considered that a substantially rectangular smart card or SIM card bearing the contact plate on its front face has the shape key at the bottom right of this card. By extension, the opposite face to the front face is the back face. It is possible to define the contacts C1 and C5 as being situated close to the upper edge (or at the top) of the card or of the contact plate, the contacts C4 and C8 as being situated close to the lower edge (or at the bottom), the contacts C1 to C4 as being close to the left edge and the contacts C5 to C8 as being situated close to the right edge.
A new smart card format has recently been developed wherein the dimensions and thickness are smaller than those of the card with the 3FF format. To do this, the contacts C4 and C8 have been moved between the columns of contacts C1 to C3 and C5 to C7 (see the as yet unpublished application PCT/FR2012/051292). The contact surfaces C1 to C3 and C5 to C7 are compliant with the contact areas of the ISO7816 standard. This new format, which can also be called microSIM (another possible name is 4FF), may comprise a card body delimited by a rectangular shape of 8.8 mm×12.3 mm×0.70 mm, with a shape key of 1.65×1.65 mm in one corner of the card body.
The tolerances of all the cards described above are in the order of 0.1 mm.
In order to render the various cards mutually compatible, card adapters exist that make it possible to convert a card into a different format. Thus a card can be read by a reading device initially provided for a card in a different format. For example, there are adapters for converting a card with the 3FF format into the 2FF format. Such an adapter can comprise a body whose dimensions are those of a 2FF card. The body comprises a recess shaped to receive a card with the 3FF format. The recess is formed so that the body of the adapter can surround the recess in order to ensure the rigidity of the adapter and/or the adapter plus card assembly. The recess is configured so that once the 3FF card is inserted into the 2FF adapter, the contact surfaces of the card with the 3FF format are compatible with the ISO contact areas of the card with the 2FF format.
It is desirable to make the contact surfaces of a card with a format whose outer dimensions are smaller than the 3FF format compatible, so that a card reader, for example with the 3FF format, can read at least the contacts C1 to C3 and C5 to C7. This compatibility can be achieved by way of an adapter, which can have mechanical stability problems with regard to the current configuration of the contact surfaces and areas.
The reason is that the contact areas C1 and C5 of a card in a format whose dimensions are smaller than the dimensions of a card with the 3FF format (for example the 4FF format previously mentioned in relation to the as yet unpublished application PCT/FR2012/051292) are in practice situated substantially 1.01 millimeters from the upper edge. The contact areas C1 and C5 of a card with the 3FF format are situated a maximum of 1.34 millimeters from the upper edge. This means that an arm with a width of substantially 330 micrometers of material is left for constituting the upper edge of the adapter. It is easily understood that an arm with such a small width can have mechanical stability problems, particularly during the operations of assembly and/or disassembly of the card and its adapter.
Such an adapter can therefore give rise to problems of mechanical stability and notably of robustness and/or of stretching and/or of breaking of the material.